Inoculation of mice with coxsackievirus B3 (CVB3) results in myocarditis, a focal mononuclear cell inflammatory response to virus-infected cells in heart tissue. Delayed hypersensitivity responses involving cytotoxic T lymphocyte (CTL) reactions to viral-induced surface antigens (neoantigen(s) are implicated in this excellent model for the human disease. We propose to use specific immunofluorescence assays to identify the cells in heart tissue that become infected and bear the neoantigen(s) and the mononuclear cell types that respond to neoantigen(s) during formation of myocarditic lesions. Murine neonatal skin fibroblasts (MNSF) infected with CVB3 serve as targets for CTL from CVB3-inoculated myocarditic mice, indicating the presence of neoantigen(s). We will use MNSF as a tissue culture source for neoantigen(s) and identify, isolate and characterize the neoantigen(s) by a variety of biochemical and immunological techniques. Monoclonal antibodies will be developed against MNSF neoantigen(s) for use in studies on temporal appearance of neoantigen(s) on the surface of MNSF relative to virus replication, genetic origin, type of heart cell expressing the neoantigen(s) and role of neoantigen(s) in the disease process. We will identify and determine the mechanism of action of a factor(s) in sera from mice resistant to CVB3-induced myocarditis which can, upon transfer to normal mice, confer protection. We will investigate the mechanism by which anti-idiotypic antiserum against anti-CVB3 antibody prophylactically ameliorates CVB3-induced myocarditis. The mechanism of action of an antimyocarditic base analogue will be assessed. The possible role of suppressor cells in preventing myocarditis will be examined using x-irradiated murine donors or recipients and lymphocytes from several types of mice resistant to CVB3-induction of myocarditis. In all of the above studies, a unique collection of isogenic amyocarditic or myocarditic variants of CVB3 will be used to provide information on the nature of the neoantigen(s), the possible role of suppressor cells and the types of mononuclear cells participating in myocarditis. We will use biochemical methods to determine whether differences in virulence between amyocarditic and myocarditic variants of CVB3 can be attributed to differences in a capsid polypeptide(s).